Keep only the variables from the input listed in selections

srckeep(diskf, selections, ...)

Arguments

diskf: a disk.frame
selections: The list of variables to keep from the input source
...: not yet used

Examples

cars.df = as.disk.frame(cars)

# when loading cars's chunks into RAM, load only the column speed
collect(srckeep(cars.df, "speed"))
#>     speed
#>  1:     4
#>  2:     4
#>  3:     7
#>  4:     7
#>  5:     8
#>  6:     9
#>  7:    10
#>  8:    10
#>  9:    10
#> 10:    11
#> 11:    11
#> 12:    12
#> 13:    12
#> 14:    12
#> 15:    12
#> 16:    13
#> 17:    13
#> 18:    13
#> 19:    13
#> 20:    14
#> 21:    14
#> 22:    14
#> 23:    14
#> 24:    15
#> 25:    15
#> 26:    15
#> 27:    16
#> 28:    16
#> 29:    17
#> 30:    17
#> 31:    17
#> 32:    18
#> 33:    18
#> 34:    18
#> 35:    18
#> 36:    19
#> 37:    19
#> 38:    19
#> 39:    20
#> 40:    20
#> 41:    20
#> 42:    20
#> 43:    20
#> 44:    22
#> 45:    23
#> 46:    24
#> 47:    24
#> 48:    24
#> 49:    24
#> 50:    25
#>     speed

# clean up cars.df
delete(cars.df)